Force measuring device

ABSTRACT

A force measuring device for measuring forces between mutually parallel machine parts, preferably in force bypass. The device has two mutually parallel abutment faces (5,6) having an adjustable distance between them. A force sensor (18) is integrated in a first measuring wedge (1), with a first measuring face projecting beyond the measuring wedge (1) and forming the first abutment face (5). On the side opposite the abutment face (5) is a first force-transmitting inclined slide face (15). A second measuring wedge (3) comprises a second force-transmitting slide face (16) being parallel to the first slide face (15). On the side opposite the second slide face (15) is the second abutment face (6) being parallel to the first abutment face (5). The measuring wedges (1,3) can slide relative to each other on the slide faces (15,16) thereby causing the abutment faces (5,6) to move parallel to each other. The wedges (1,3) are connected to each other by an adjustment device (7,8).

FIELD OF THE INVENTION

The invention relates to a force measuring device comprising a forcesensor for measuring forces between mutually parallel machine parts,preferably in force bypass, in which the force measuring device has twoparallel abutment faces having an adjustable distance between them.

DESCRIPTION OF THE PRIOR ART

Force measuring devices of the above type are used for the measurementof forces in machines, particularly machine tools, and preferably inforce bypass. Measurement in force bypass is known from CH-PS 476 990and DE 27 36 373 A1. If the measurement is performed in force bypass,the force sensor need measure only part of the generated forces so thatthe measurement range can be considerably widened.

Known from EP 0 433 535 A are force measuring devices which comprise atleast one force sensor and, to perform measurement in force bypass, areclamped in pocket-sized recesses between two machine parts. For thispurpose, it is known to provide the force measuring device with pairs ofwedges which make it possible to install the force measuring devicewhile providing with a bias. However, known measuring devices have sucha constructional height that they cannot be mounted in partition plateshaving a thickness of 12 mm, since the pair of wedges together with themeasuring element has a thickness of about 16 mm. On the other hand, thecommonly used partition plates or respectively force measuring plateshave a thickness of 12 mm. Such partition plates are installed, e.g.,between the tool revolver and the tool carriage in turning machines soas to perform tool or process monitoring. To receive the force measuringdevice, the partition plates have corresponding recesses formed therein.Further, known force measuring devices disadvantageously consist of aplurality of constructional parts so that they are mounted withdifficulties. Some of the known force measuring devices have to befastened to the machine parts or be supported against them to allow thesetting of the bias force. Also this is undesired with regard to astraightforward mounting process.

SUMMARY OF THE INVENTION

It is the object of the invention to provide a force measuring devicewhich has a reduced constructional height, can be mounted in an easiermanner and is suited for a larger variety of uses.

The invention advantageously provides that the force sensor in a firstmeasuring wedge is integrated in a recess in such a manner that theforce sensor projects beyond the first measuring wedge, together with afirst measuring surface forms a first abutment face, and with the secondmeasuring surface, being parallel to the first measuring surface, issupported in the recess, that the first measuring wedge on the sideopposite to the abutment face comprises a first force-transmittinginclined slide face, that a second flat measuring wedge comprises asecond force-transmitting slide face being parallel to the first slideface and on the side opposite the second slide face comprises a secondabutment face being parallel to the first abutment face, and that themeasuring wedges are in parallel displaceable relative to each other onthe abutment faces by use of an adjustment device and are connected toeach other via said adjustment device.

Such a construction allows for a space-saving arrangement since thefirst measuring wedge need not be substantially higher than the forcesensor, while the second measuring wedge can have a flat configuration.A further considerable advantage resides in that the force measuringdevice is arranged in one piece. Thereby, the mounting process can beperformed in a very convenient manner and also can be easily performedsubsequently. The inventive construction allows for a total height ofthe force measuring device which is not substantially larger than theminimum height determined by the force sensor. Thus, it is possible toproduce force measuring devices having a constructional height of 12 mm,which can be used also in standardized partition plates to carry outforce measurement between two machine parts.

Preferably, it is provided that the second measuring wedge accommodatesthe first measuring wedge in a recess which is delimited by at least twoside walls. Thus, the slide face of the second measuring wedge can beextended until merging into the second abutment face of the secondmeasuring wedge. In this regard, the side walls serve for increasing thestability so that the second slide face at its tapered free end isprotected against damage. A laterally stiffened slide face of this typeallows for a reduction of the minimal wall thickness and thus of theconstructional height of the force measuring device.

The adjustment device is preferably arranged in a transverse wallextending orthogonally to the side walls, and is most preferablyarranged at the higher end of the second slide face. The adjustmentdevice makes it possible to set a bias between the abutment faces 5,6 ina pocket-shaped recess between two mutually parallel machine parts,while it is not required that elements of the adjustment device besupported against the machine parts 10,12.

The angle of inclination of the slide faces is about 3° to 9°,preferably about 6°.

The insertion of the measuring wedge into a recess delimited by two sidewalls and at least one transverse wall offers the advantage that, inspite of the reduced dimensions of the constructional element, there isprovided a stable and stiff force measuring device which can be loadedto a large extent.

An embodiment of the invention will be explained in greater detailhereunder with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross sectional view of a force measuring deviceaccording to the invention,

FIG. 2 shows a view of the rear end face of the force measuring device,

FIG. 3 shows a plan view of the force measuring device of FIG. 1,

FIG. 4 illustrates the mounting of the force measuring device into apartition plate, and

FIG. 5 is a view of a force measuring device clamped between two machineparts in a recess.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The force measuring device substantially consists of two cooperatingmeasuring wedges 1,3, an adjustment device allowing a paralleldisplacement 9 of the measuring wedges 1,3 relative to each other, and aforce sensor 18 which in the first measuring wedge is integrated in arecess 13. The recess accommodating the force sensor is arranged in thehigher portion of measuring wedge 1, and the force sensor 18 with afirst measuring face 11 projects beyond the measuring wedge 1 and withits measuring face 11 forms a first abutment face 5 of the forcemeasuring device. The force sensor 18 is supported on its side oppositethe measuring face 11 by a second measuring surface 14. Support for thisaddition is found in FIG. 1 and claim 3. In its unloaded condition, theforce sensor 18 projects beyond the upper face 19 of measuring wedge 1parallel to abutment face 5 to an extent corresponding to the maximumadmissible compression, thus also providing an overload safety devicefor the force sensor 18. The abutment face 5 extends in parallel to thesurfaces of mutually parallel machine parts 10,12 between which theforce is to be measured. The constructional height of the measuringwedge 1 need not be substantially larger than the constructional heightof the force sensor 18. Therefore, the measuring wedge 1 shown in FIG. 1could still be reduced in size to such an extent that the inclination ofthe slide face 15 on the underside of measuring wedge 1 extends to aposition close to the recess 13 for the force sensor 18.

In FIGS. 1 and 2, the force measuring device is illustrated in thedisassembled state.

According to FIG. 2, however, the upper measuring wedge 1 is fixedlyconnected to the lower measuring wedge 3 through the adjustment device7,8, so that the parts cannot fall apart during the mounting process.The lower measuring wedge 3 comprises a recess, delimited by atransverse wall 2 and two mutually parallel side walls 4, whichslideably receives the upper measuring wedge 1 on a lower slide face 16of lower measuring wedge 3 being parallel to the first slide face 15 ofupper measuring wedge 1.

The angle of inclination of the mutually parallel slide faces 15,16 isabout 3° to 9°, preferably about 6°.

The adjustment device comprises at least one clamping screw 7 and arelease or respectively press-on screw 8 which is guided through thetransverse wall 2 in parallel to the moving direction 9 of measuringwedge 1. By use of the adjustment device, the upper measuring wedge 1can be displaced on the force-transmitting slide faces 15,16 in themoving direction 9 parallel to the side walls 4, whereby the distancebetween the abutment faces 5 and 6 is changed and a predetermined biasforce between the machine parts 10,12 can be set.

The lower abutment face 6 of second measuring wedge 3, arranged inparallel to the abutment face 5 of force sensor 18, is supported on themachine part 12. On the end opposite to transverse wall 2, the slideface of lower measuring wedge 3 can be guided nearly to the lowerabutment face 6 because the side walls 4 lend sufficient stability tolower measuring wedge 3.

The cable connection 22 for the force sensor 18 is preferably led to theoutside on one of the short end sides of upper measuring wedge 1. Theforce sensor 18 can comprise a one-, two- or three-dimensional forcemeasuring element.

Using a 3D quartz measuring element, quasi-static and dynamic tensionmeasurements and respectively compression measurements can be performedin structures of machine parts or devices according the force bypassmeasuring principle.

FIG. 4 illustrates the mounting of the force measuring device in apartition plate 24 having recesses 26 formed therein with upper andlower openings.

FIG. 5 illustrates the mounting of the force measuring device in apocket-shaped recess 25 between two machine components 10,12.

I claim:
 1. A force measuring device comprising a force sensor (18) formeasuring forces between mutually parallel machine parts (10,12),preferably in force bypass, comprising:two mutually parallel abutmentfaces (5,6), the orthogonal distance of said abutment faces beingadjustable, a first measuring wedge (1) in which the force sensor ismounted, a second measuring wedge (3) on which the first measuring wedge(1) is placed, each measuring wedge (1,3) having mutually parallel,mutually confronting slide faces (15,16) arranged at an inclination tothe abutment faces (5,6) for permitting parallel displacement of thefirst and second abutment faces (5,6) with respect to each other, and anadjustment means (7,8) for connecting the measuring wedges (1,3) to eachother for displacing the first measuring wedge (1) relative to thesecond measuring wedge (3) to set the distance between the abutmentfaces (5,6).
 2. The force measuring device according to claim 1, whereinthe force sensor (18) in the first measuring wedge (1) is arranged in aregion of the larger height within a recess (13).
 3. The force measuringdevice of claim 1 wherein the two mutually parallel abutment faces (5,6)are comprised of a first abutment face (5) on the first measuring wedge(1) and a second abutment face (6) on the second measuring edge (3). 4.The force measuring device according to claim 1, 2, or 3 and furthercomprising a first measuring face (11) on the force sensor (18)projecting beyond the first measuring wedge (1) and forming the firstabutment face (5), the sensor 18 being supported in the measuring wedge1 on a second measuring surface (14), which is parallel to the firstmeasuring face
 11. 5. The force measuring device according to claim 4,wherein the second measuring wedge 3 receives the first measuring wedge(1) in a recess (17) which is delimited by two side walls (4) extendinglaterally of the slide faces (15,16).
 6. The force measuring deviceaccording to claim 5 wherein the recess (17) in the second measuringwedge (3) is further delimited by a transverse wall (2) through whichthe adjustment device (7,8) passes to restrict movement of the firstmeasurement wedge (1) from passing beyond said transverse wall (2). 7.The force measuring device according to claim 5 wherein the force sensor(18) comprises a plurality of piezoelectric integrated quartz plates(20) which allow a force measurement in one, two or three directionsoriented orthogonally to each other.
 8. The force measuring deviceaccording to any one of claim 5 wherein the angle of inclination of theslide faces (15,16) relative to the abutment faces (5,6) is about 3° to9°, preferably about 6°.
 9. The force measuring device according toclaim 5 and further comprising a connection cable (22) with one endconnected to the force sensor (18) and the other end leading out fromthe upper measuring wedge (1).